package com.zhou;

import java.util.Scanner;

/**
 * T8
 * 一次上一个或2个台阶，N个台阶怎么上
 *
 * @author zhouxianfeng
 * @date 2021-8-19
 */
public class T8 {

    private static int total;

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int i = in.nextInt();
        //System.out.println(Fibonacci(i));


        int[] dp = new int[i + 1];

        System.out.println(Fib(i, dp));
    }

    public static void jump(int n, int goSteps) {
        if (n - goSteps == 0) {
            total += 1;
        } else if (n - goSteps < 0) {
            return;
        }
        for (int i = 1; i <= 2; i++) {
            jump(n, goSteps + i);
        }
    }

    static int Fibonacci(int n) {
        if (n <= 1) return 1;
        return Fibonacci(n - 1) + Fibonacci(n - 2);
    }

    static int Fib(int n, int[] dp) {
        if (n <= 1) return 1;
        if (dp[n] != 0) return dp[n];
        return dp[n] = Fib(n - 1, dp) + Fib(n - 2, dp);
    }
}
